This invention relates to a vehicular lamp such as head lamp, winker or stop lamp available by bonding a lamp body made of a rubber-reinforced styrene resin to a lamp lens made of a methyl methacrylate resin or the like by the hot plate welding method; a lamp body used for the vehicular lamp; and a method for manufacturing the vehicular lamp.
As a method for bonding a lamp lens to a lamp body made of a synthetic resin, it is possible to seal them by an adhesive. A so-called hot plate welding method comprising pressing a hot plate against a lamp body made of an ordinarily employed thermoplastic resin such as an ABS resin, thereby melting a portion of the lamp body and then adhering the melted portion to a lamp lens made of a methyl methacrylate resin or the like under pressure, however, has come to be adopted from the viewpoint of environmental protection, because the hot plate welding method is, different from the sealing by an adhesive, free from the use of a solvent. In such a hot plate welding method, however, when the above-mentioned thermoplastic resin constituting a lamp body made of an ABS resin is melted by a hot plate and then the hot plate is separated from the melted resin, the melted resin is sometimes drawn out in the form of a string (which will hereinafter be called xe2x80x9cstringinessxe2x80x9d) and sticks to the surface of the molded or formed product such as lamp lens or lamp body, leading to inconvenience causing inferior appearance. For reducing the stringiness occurring in the hot plate welding method, for example, a method of adding a fluorine resin such as polytetrafluoroethylene to a thermoplastic resin constituting a lamp body such as polycarbonate or ABS resin is proposed in JP-A-9-12902 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent application). This hot plate welding method does not completely dissolve the problem of stringiness when effected under low-humidity circumstances such as those in winter.
An object of the present invention is therefore to alleviate, upon manufacturing a vehicular lamp by bonding a lamp body to a lamp lens by the hot plate welding method, the above-mentioned problem stringiness of the resin constituting the lamp body without being influenced by a change in the season or humidity.
As a result of extensive investigation to attain the above-mentioned object, it has been found that stringiness which occurs upon manufacturing a vehicular lamp by bonding a lamp body to a lamp lens by the hot plate welding method can be reduced largely even under low-humidity conditions such as in winter by molding or forming the lamp body from a resin composition obtained by adding an antistatic agent to a rubber-reinforced styrene resin and by using, as the rubber-reinforced styrene resin, a resin composition available by mixing a graft copolymer containing a specific component with a vinyl copolymer, thereby leading to the completion of the present invention.
In the present invention, there is thus provided a method for manufacturing a vehicular lamp which comprises pressing a heated hot plate against a lamp body made of a rubber-reinforced styrene resin, thereby melting a portion of the lamp body and then adhering the melted portion to a lamp lens under pressure, thereby bonding the lamp body to the lamp lens, wherein the lamp body is molded or formed from a resin composition obtained by adding 0.1 to 5 parts by weight of an antistatic agent to 100 parts by weight of a rubber-reinforced styrene resin and in particular, a resin composition (C) composed mainly of 100 to 10 parts by weight of the following graft copolymer (A) and 0 to 90 parts by weight of the following vinyl copolymer (B), 100 parts by weight in total, is used as the rubber-reinforced styrene resin:
(A) a graft copolymer obtained by graft polymerization of 80 to 5 parts by weight of a monomer mixture to 20 to 95 parts by weight of a rubbery polymer, said monomer mixture containing 99.9 to 60 wt. % of at least one vinyl compound selected from the group consisting of vinyl cyanide compounds, aromatic vinyl compounds and alkyl (meth)acrylate compounds, 0 to 30 wt. % of another vinyl compound copolymerizable therewith and 0.1 to 40 wt. % of a glycidyl ester compound of an xcex1,xcex2-unsaturated acid; and
(B) a vinyl copolymer obtained by the reaction of 10 to 40 wt. % of a vinyl cyanide compound, 60 to 90 wt. % of an aromatic vinyl compound and 0 to 30 wt. % of another vinyl compound copolymerizable therewith.
Upon manufacturing a vehicular lamp under low-humidity circumstances such as winter by pressing a heated hot plate against a lamp body, thereby melting a portion of the lamp body and then adhering the melted portion to a lamp lens under pressure, thereby bonding the lamp body to the lamp lens, the use of a rubber-reinforced styrene resin obtained by adding thereto an antistatic agent according to the present invention makes it possible to largely reduce the stringiness of the resin which constitutes the lamp body, compared with the use of a rubber-reinforced styrene resin conventionally employed as a material for a lamp body. This method is particularly useful for the manufacture of vehicular lamps such as head lamp, winker and stop lamp.